Renault Grand Espace Non Start

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Hi just throwing this out here for pointers as I'm missing something

OK I have the grand espace v6 3.0 diesel

 

Over the holiday I removed the engine and changed the head gaskets

I have put the engine back in but now it won't start

it starts for a second then cuts out

it gives a fault code of cam sensor with 3 examples

1- cam sensor open circuit

2- cam sensor signal incomprehensible

3- cam sensor signal incomprehensible with engine speed

 

So I have checked - cam timing , pump timing , all top dead centre marks ,

Removed timing belt again and again checked everything is lined up via auto data

replaced both crank and cam sensors

made a part loom from sensors to ECU ( it is a renault )

And still I get this fault code

I have tried new feeds to sensors

and independent earth's

the sensors are quite simple as in two wires - signal and earth

the car drove to my lockup (but was pushing water from header hence head gaskets )

I'm now lost

I'm missing something -but just can't see it

the fault code was not present before removing engine